Method and device for transmitting data by using spatial modulation scheme in wireless access system

ABSTRACT

The present invention provides methods for transmitting and receiving data and control signals by applying a spatial modulation scheme to a wireless access system, and devices for supporting same. The method whereby a transmitter transmits data signals by using a spatial modulation (SM) scheme in a wireless access system, according to one embodiment of the present invention, may comprise the steps of: selecting two or more transmission antennas for transmitting the data signals; deriving data bit strings for selecting the two or more transmission antennas; configuring the data signals by using the SM scheme on the basis of the data bit strings; and transmitting the configured data signals via the selected two or more transmission antennas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2014/007827, filed on Aug. 22, 2014, which claims the benefit of U.S. Provisional Application No. 61/868,595, filed on Aug. 22, 2013, the contents of which are all hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a method for transmitting and receiving data and control signals by applying a spatial modulation scheme to a wireless access system and a device for supporting the same.

BACKGROUND ART

Wireless access systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless access system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.) among them. For example, multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.

DISCLOSURE Technical Problem

An object of the present invention is to provide methods for efficiently transmitting and receiving data.

Another object of the present invention is to provide methods for applying a spatial modulation (SM) scheme for efficient data transmission and reception.

Still another object of the present invention is to provide methods for transmitting control information by using a spatial modulation scheme for efficient transmission and reception of control information.

Further still another object of the present invention is to provide devices for supporting the aforementioned methods.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Technical Solution

The present invention relates to a method for transmitting and receiving data and control signals by applying a spatial modulation scheme to a wireless access system and devices for supporting the same.

In one aspect of the present invention, a method for transmitting data signals from a transmitter by using a spatial modulation (SM) scheme in a wireless access system comprises the steps of selecting two or more transmitting antennas for transmitting the data signals; deriving data bit streams for selecting the two or more transmitting antennas; configuring the data signals by using the SM scheme on the basis of the data bit streams; and transmitting the configured data signals through the selected two or more transmitting antennas.

The method may further comprise the step of transmitting information on a rank for transmitting the configured data signals if the rank is 2 or more. At this time, the configured data signals may be transmitted together with a UE specific reference signal matched with each of the two or more transmitting antennas. Also, the configured data signals may be E-PDCCH (Enhanced-Physical Downlink Control Channel) signals which are control information transmitted from a data region. Also, an ACK/NACK signal, a new data indicator (NDI) or transmission power control (TPC) information may be mapped into the data bit streams.

Otherwise, systematic bits of input bits may be mapped into the data bits for selecting the two or more antennas.

Otherwise, parity bits of input bits may be mapped into the data bits for selecting the two or more antennas.

In another aspect of the present invention, a method for receiving data signals in a receiver by using a spatial modulation (SM) scheme in a wireless access system comprises the steps of detecting an antenna port of a transmitter, to which the received data signals are transmitted; deriving data bit streams meant by the antenna port; and demodulating the received data signals on the basis of the data bit streams, wherein the data bit streams mean bit streams used by the transmitter to select the antenna port.

The method may further comprise the step of receiving information on a rank of the received data signals. At this time, the received data signals may be transmitted together with a UE specific reference signal matched with a transmitting antenna of the transmitter. The received data signals may be E-PDCCH (Enhanced-Physical Downlink Control Channel) signals which are control information transmitted from a data region. Also, a ACK/NACK signal, a new data indicator (NDI) or transmission power control (TPC) information may be mapped into the data bit streams.

Otherwise, systematic bits of input bits may be mapped into the data bit streams. Otherwise, parity bits of input bits may be mapped into the data bit streams.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Advantageous Effects

As is apparent from the above description, the embodiments of the present invention have the following effects.

First of all, additional data or control information can be transmitted with a small number of bits, whereby data can be transmitted and received efficiently.

Secondly, data signals can be transmitted together with control information.

Thirdly, systematic bits or parity bits can be matched with bit streams used for antenna selection during transmission of the data signals, whereby more reliable data transmission can be performed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

FIG. 1 is a conceptual diagram illustrating physical channels used in the embodiments and a signal transmission method using the physical channels.

FIG. 2 is a diagram illustrating a structure of a radio frame for use in the embodiments.

FIG. 3 is a diagram illustrating an example of a resource grid of a downlink slot according to the embodiments.

FIG. 4 is a diagram illustrating a structure of an uplink subframe according to the embodiments.

FIG. 5 is a diagram illustrating a structure of a downlink subframe according to the embodiments.

FIG. 6 is a diagram illustrating an example of a component carrier (CC) used in the embodiments of the present invention and carrier aggregation used in an LTE-A system.

FIG. 7 is a diagram illustrating a subframe frame structure of an LTE-A system according to cross carrier scheduling used in the embodiments of the present invention;

FIG. 8 is a diagram illustrating physical mapping of a PUCCH format into PUCCH RBs.

FIG. 9 is a diagram illustrating PUCCH formats 2/2a/2b in case of a normal cyclic prefix.

FIG. 10 is a diagram illustrating PUCCH formats 2/2a/2b in case of an extended cyclic prefix.

FIG. 11 is a diagram illustrating PUCCH formats 1a/1b in case of a normal cyclic prefix.

FIG. 12 is a diagram illustrating PUCCH formats 1a/1b in case of an extended cyclic prefix.

FIG. 13 is a diagram illustrating one of constellation mapping of HARQ ACK/NACK for a normal CP.

FIG. 14 is a diagram illustrating joint coding performed for HARQ ACK/NACK and CQI for an extended CP.

FIG. 15 is a diagram illustrating one of methods for multiplexing SR and ACK/NACK signal.

FIG. 16 is a diagram illustrating constellation mapping of ACK/NACK and SR for PUCCH formats 1/1a/1b.

FIG. 17 is a diagram illustrating methods of matching control information with a physical resource region.

FIG. 18 is a diagram illustrating an example of a coding method based on a dual RM scheme.

FIG. 19 is a diagram illustrating a method for interleaving output code bits when dual RM described in FIG. 18 is used.

FIG. 20 is a diagram illustrating a concept of a spatial modulation scheme.

FIG. 21 is a diagram illustrating one of methods for transmitting and receiving data/control signals by using a spatial modulation (SM) scheme to which spatial multiplexing is applied.

FIG. 22 is a diagram illustrating a method for applying a spatial modulation (SM) scheme to systematic bits and parity bits, which configure data signals.

FIG. 23 is a diagram illustrating one of methods for configuring data signals in a transmitter by applying a spatial modulation (SM) scheme.

FIG. 24 is a diagram illustrating examples of methods for transmitting turbo code bits by applying a spatial modulation (SM) scheme to the turbo code bits.

FIG. 25 is a diagram illustrating a device through which methods described in FIG. 1 to FIG. 24 can be embodied.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention described in detail hereinafter relate to methods for transmitting and receiving data and control signals by using a spatial modulation scheme and devices for supporting the same.

The embodiments of the present disclosure described below are combinations of elements and features of the present disclosure in specific forms. The elements or features may be considered selective unless otherwise mentioned. Each element or feature may be practiced without being combined with other elements or features. Further, an embodiment of the present disclosure may be constructed by combining parts of the elements and/or features. Operation orders described in embodiments of the present disclosure may be rearranged. Some constructions or elements of any one embodiment may be included in another embodiment and may be replaced with corresponding constructions or features of another embodiment.

In the description of the attached drawings, a detailed description of known procedures or steps of the present disclosure will be avoided lest it should obscure the subject matter of the present disclosure. In addition, procedures or steps that could be understood to those skilled in the art will not be described either.

Throughout the specification, when a certain portion “includes” or “comprises” a certain component, this indicates that other components are not excluded and may be further included unless otherwise noted. The terms “unit”, “-or/er” and “module” described in the specification indicate a unit for processing at least one function or operation, which may be implemented by hardware, software or a combination thereof. In addition, the terms “a or an”, “one”, “the” etc. may include a singular representation and a plural representation in the context of the present invention (more particularly, in the context of the following claims) unless indicated otherwise in the specification or unless context clearly indicates otherwise.

In the embodiments of the present disclosure, a description is mainly made of a data transmission and reception relationship between a Base Station (BS) and a User Equipment (UE). A BS refers to a terminal node of a network, which directly communicates with a UE. A specific operation described as being performed by the BS may be performed by an upper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality of network nodes including a BS, various operations performed for communication with a UE may be performed by the BS, or network nodes other than the BS. The term ‘BS’ may be replaced with a fixed station, a Node B, an evolved Node B (eNode B or eNB), an Advanced Base Station (ABS), an access point, etc.

In the embodiments of the present disclosure, the term terminal may be replaced with a UE, a Mobile Station (MS), a Subscriber Station (SS), a Mobile Subscriber Station (MSS), a mobile terminal, an Advanced Mobile Station (AMS), etc.

A transmitter is a fixed and/or mobile node that provides a data service or a voice service and a receiver is a fixed and/or mobile node that receives a data service or a voice service. Therefore, a UE may serve as a transmitter and a BS may serve as a receiver, on an UpLink (UL). Likewise, the UE may serve as a receiver and the BS may serve as a transmitter, on a DownLink (DL).

The embodiments of the present disclosure may be supported by standard specifications disclosed for at least one of wireless access systems including an Institute of Electrical and Electronics Engineers (IEEE) 802.xx system, a 3^(rd) Generation Partnership Project (3GPP) system, a 3GPP Long Term Evolution (LTE) system, and a 3GPP2 system. In particular, the embodiments of the present disclosure may be supported by the standard specifications, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.321 and 3GPP TS 36.331. That is, the steps or parts, which are not described to clearly reveal the technical idea of the present disclosure, in the embodiments of the present disclosure may be explained by the above standard specifications. All terms used in the embodiments of the present disclosure may be explained by the standard specifications.

Reference will now be made in detail to the embodiments of the present disclosure with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present disclosure, rather than to show the only embodiments that can be implemented according to the invention.

The following detailed description includes specific terms in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the specific terms may be replaced with other terms without departing the technical spirit and scope of the present disclosure.

For example, an antenna refers to a physical antenna, and an antenna port is a logic concept matched with a specific physical antenna. However, in the embodiments of the present invention, the antenna and the antenna port may be used to refer to the same meaning unless specially described.

Hereinafter, 3GPP LTE/LTE-A systems which are examples of a wireless access system which can be applied to embodiments to the present invention will be explained.

The embodiments of the present disclosure can be applied to various wireless access systems such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), etc.

CDMA may be implemented as a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented as a radio technology such as Global System for Mobile communications (GSM)/General packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA (E-UTRA), etc.

UTRA is a part of Universal Mobile Telecommunications System (UMTS). 3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMA for DL and SC-FDMA for UL. LTE-Advanced (LTE-A) is an evolution of 3GPP LTE. While the embodiments of the present disclosure are described in the context of a 3GPP LTE/LTE-A system in order to clarify the technical features of the present disclosure, the present disclosure is also applicable to an IEEE 802.16e/m system, etc.

1. 3GPP LTE/LTE-A System

In a wireless access system, a UE receives information from an eNB on a DL and transmits information to the eNB on a UL. The information transmitted and received between the UE and the eNB includes general data information and various types of control information. There are many physical channels according to the types/usages of information transmitted and received between the eNB and the UE.

1.1 System Overview

FIG. 1 illustrates physical channels and a general method using the physical channels, which may be used in embodiments of the present disclosure.

When a UE is powered on or enters a new cell, the UE performs initial cell search (S11). The initial cell search involves acquisition of synchronization to an eNB. Specifically, the UE synchronizes its timing to the eNB and acquires information such as a cell Identifier (ID) by receiving a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S-SCH) from the eNB.

Then the UE may acquire information broadcast in the cell by receiving a Physical Broadcast Channel (PBCH) from the eNB.

During the initial cell search, the UE may monitor a DL channel state by receiving a Downlink Reference Signal (DL RS).

After the initial cell search, the UE may acquire more detailed system information by receiving a Physical Downlink Control Channel (PDCCH) and receiving a Physical Downlink Shared Channel (PDSCH) based on information of the PDCCH (S12).

To complete connection to the eNB, the UE may perform a random access procedure with the eNB (S13 to S16). In the random access procedure, the UE may transmit a preamble on a Physical Random Access Channel (PRACH) (S13) and may receive a PDCCH and a PDSCH associated with the PDCCH (S14). In the case of contention-based random access, the UE may additionally perform a contention resolution procedure including transmission of an additional PRACH (S15) and reception of a PDCCH signal and a PDSCH signal corresponding to the PDCCH signal (S16).

After the above procedure, the UE may receive a PDCCH and/or a PDSCH from the eNB (S17) and transmit a Physical Uplink Shared Channel (PUSCH) and/or a Physical Uplink Control Channel (PUCCH) to the eNB (S18), in a general UL/DL signal transmission procedure.

Control information that the UE transmits to the eNB is generically called Uplink Control Information (UCI). The UCI includes a Hybrid Automatic Repeat and reQuest Acknowledgement/Negative Acknowledgement (HARQ-ACK/NACK), a Scheduling Request (SR), a Channel Quality Indicator (CQI), a Precoding Matrix Index (PMI), a Rank Indicator (RI), etc.

In the LTE system, UCI is generally transmitted on a PUCCH periodically. However, if control information and traffic data should be transmitted simultaneously, the control information and traffic data may be transmitted on a PUSCH. In addition, the UCI may be transmitted aperiodically on the PUSCH, upon receipt of a request/command from a network.

FIG. 2 illustrates exemplary radio frame structures used in embodiments of the present disclosure.

FIG. 2(a) illustrates frame structure type 1. Frame structure type 1 is applicable to both a full Frequency Division Duplex (FDD) system and a half FDD system.

One radio frame is 10 ms (Tf=307200·Ts) long, including equal-sized 20 slots indexed from 0 to 19. Each slot is 0.5 ms (Tslot=15360·Ts) long. One subframe includes two successive slots. An ith subframe includes 2ith and (2i+1)th slots. That is, a radio frame includes 10 subframes. A time required for transmitting one subframe is defined as a Transmission Time Interval (TTI). Ts is a sampling time given as Ts=1/(15 kHz×2048)=3.2552×10−8 (about 33 ns). One slot includes a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols or SC-FDMA symbols in the time domain by a plurality of Resource Blocks (RBs) in the frequency domain.

A slot includes a plurality of OFDM symbols in the time domain. Since OFDMA is adopted for DL in the 3GPP LTE system, one OFDM symbol represents one symbol period. An OFDM symbol may be called an SC-FDMA symbol or symbol period. An RB is a resource allocation unit including a plurality of contiguous subcarriers in one slot.

In a full FDD system, each of 10 subframes may be used simultaneously for DL transmission and UL transmission during a 10-ms duration. The DL transmission and the UL transmission are distinguished by frequency. On the other hand, a UE cannot perform transmission and reception simultaneously in a half FDD system.

The above radio frame structure is purely exemplary. Thus, the number of subframes in a radio frame, the number of slots in a subframe, and the number of OFDM symbols in a slot may be changed.

FIG. 2(b) illustrates frame structure type 2. Frame structure type 2 is applied to a Time Division Duplex (TDD) system. One radio frame is 10 ms (Tf=307200·Ts) long, including two half-frames each having a length of 5 ms (=153600·Ts) long. Each half-frame includes five subframes each being 1 ms (=30720·Ts) long. An ith subframe includes 2ith and (2i+1)th slots each having a length of 0.5 ms (Tslot=15360·Ts). Ts is a sampling time given as Ts=1/(15 kHz×2048)=3.2552×10−8 (about 33 ns).

A type-2 frame includes a special subframe having three fields, Downlink Pilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot (UpPTS). The DwPTS is used for initial cell search, synchronization, or channel estimation at a UE, and the UpPTS is used for channel estimation and UL transmission synchronization with a UE at an eNB. The GP is used to cancel UL interference between a UL and a DL, caused by the multi-path delay of a DL signal.

[Table 1] below lists special subframe configurations (DwPTS/GP/UpPTS lengths).

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix in downlink UpPTS UpPTS Normal Extended Normal Extended Special subframe cyclic prefix cyclic prefix cyclic prefix cyclic prefix configuration DwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 · T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL resource grid for the duration of one DL slot, which may be used in embodiments of the present disclosure.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols in the time domain. One DL slot includes 7 OFDM symbols in the time domain and an RB includes 12 subcarriers in the frequency domain, to which the present disclosure is not limited.

Each element of the resource grid is referred to as a Resource Element (RE). An RB includes 12×7 REs. The number of RBs in a DL slot, NDL depends on a DL transmission bandwidth. A UL slot may have the same structure as a DL slot.

FIG. 4 illustrates a structure of a UL subframe which may be used in embodiments of the present disclosure.

Referring to FIG. 4, a UL subframe may be divided into a control region and a data region in the frequency domain. A PUCCH carrying UCI is allocated to the control region and a PUSCH carrying user data is allocated to the data region. To maintain a single carrier property, a UE does not transmit a PUCCH and a PUSCH simultaneously. A pair of RBs in a subframe are allocated to a PUCCH for a UE. The RBs of the RB pair occupy different subcarriers in two slots. Thus it is said that the RB pair frequency-hops over a slot boundary.

FIG. 5 illustrates a structure of a DL subframe that may be used in embodiments of the present disclosure.

Referring to FIG. 5, up to three OFDM symbols of a DL subframe, starting from OFDM symbol 0 are used as a control region to which control channels are allocated and the other OFDM symbols of the DL subframe are used as a data region to which a PDSCH is allocated. DL control channels defined for the 3GPP LTE system include a Physical Control Format Indicator Channel (PCFICH), a PDCCH, and a Physical Hybrid ARQ Indicator Channel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe, carrying information about the number of OFDM symbols used for transmission of control channels (i.e. the size of the control region) in the subframe. The PHICH is a response channel to a UL transmission, delivering an HARQ ACK/NACK signal. Control information carried on the PDCCH is called Downlink Control Information (DCI). The DCI transports UL resource assignment information, DL resource assignment information, or UL Transmission (Tx) power control commands for a UE group.

1.2 Physical Downlink Control Channel (PDCCH)

1.2.1 PDCCH Overview

The PDCCH may deliver information about resource allocation and a transport format for a Downlink Shared Channel (DL-SCH) (i.e. a DL grant), information about resource allocation and a transport format for an Uplink Shared Channel (UL-SCH) (i.e. a UL grant), paging information of a Paging Channel (PCH), system information on the DL-SCH, information about resource allocation for a higher-layer control message such as a random access response transmitted on the PDSCH, a set of Tx power control commands for individual UEs of a UE group, Voice Over Internet Protocol (VoIP) activation indication information, etc.

A plurality of PDCCHs may be transmitted in the control region. A UE may monitor a plurality of PDCCHs. A PDCCH is transmitted in an aggregate of one or more consecutive Control Channel Elements (CCEs). A PDCCH made up of one or more consecutive CCEs may be transmitted in the control region after subblock interleaving. A CCE is a logical allocation unit used to provide a PDCCH at a code rate based on the state of a radio channel. A CCE includes a plurality of RE Groups (REGs). The format of a PDCCH and the number of available bits for the PDCCH are determined according to the relationship between the number of CCEs and a code rate provided by the CCEs.

1.2.2 PDCCH Structure

A plurality of PDCCHs for a plurality of UEs may be multiplexed and transmitted in the control region. A PDCCH is made up of an aggregate of one or more consecutive CCEs. A CCE is a unit of 9 REGs each REG including 4 REs. Four Quadrature Phase Shift Keying (QPSK) symbols are mapped to each REG. REs occupied by RSs are excluded from REGs. That is, the total number of REGs in an OFDM symbol may be changed depending on the presence or absence of a cell-specific RS. The concept of an REG to which four REs are mapped is also applicable to other DL control channels (e.g. the PCFICH or the PHICH). Let the number of REGs that are not allocated to the PCFICH or the PHICH be denoted by NREG. Then the number of CCEs available to the system is NCCE (=└N_(REG)/9┘) and the CCEs are indexed from 0 to NCCE−1.

To simplify the decoding process of a UE, a PDCCH format including n CCEs may start with a CCE having an index equal to a multiple of n. That is, given CCE the PDCCH format may start with a CCE satisfying i mod n=0.

The eNB may configure a PDCCH with 1, 2, 4, or 8 CCEs. {1, 2, 4, 8} are called CCE aggregation levels. The number of CCEs used for transmission of a PDCCH is determined according to a channel state by the eNB. For example, one CCE is sufficient for a PDCCH directed to a UE in a good DL channel state (a UE near to the eNB). On the other hand, 8 CCEs may be required for a PDCCH directed to a UE in a poor DL channel state (a UE at a cell edge) in order to ensure sufficient robustness.

[Table 2] below illustrates PDCCH formats. 4 PDCCH formats are supported according to CCE aggregation levels as illustrated in [Table 2].

TABLE 2 PDCCH Number of Number of Number of format CCEs (n) REGs PDCCH bits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

A different CCE aggregation level is allocated to each UE because the format or Modulation and Coding Scheme (MCS) level of control information delivered in a PDCCH for the UE is different. An MCS level defines a code rate used for data coding and a modulation order. An adaptive MCS level is used for link adaptation. In general, three or four MCS levels may be considered for control channels carrying control information.

Regarding the formats of control information, control information transmitted on a PDCCH is called DCI. The configuration of information in PDCCH payload may be changed depending on the DCI format. The PDCCH payload is information bits. [Table 3] lists DCI according to DCI formats.

TABLE 3 DCI Format Description Format 0 Resource grants for the PUSCH transmissions (uplink) Format 1 Resource assignments for single codeword PDSCH transmissions (transmission modes 1, 2 and 7) Format 1A Compact signaling of resource assignments for single codeword PDSCH (all modes) Format 1B Compact resource assignments for PDSCH using rank-1 closed loop precoding (mode 6) Format 1C Very compact resource assignments for PDSCH (e.g. paging/broadcast system information) Format 1D Compact resource assignments for PDSCH using multi- user MIMO (mode 5) Format 2 Resource assignments for PDSCH for closed-loop MIMO operation (mode 4) Format 2A Resource assignments for PDSCH for open-loop MIMO operation (mode 3) Format 3/3A Power control commands for PUCCH and PUSCH with 2-bit/1-bit power adjustment Format 4 Scheduling of PUSCH in one UL cell with multi-antenna port transmission mode

Referring to [Table 3], the DCI formats include Format 0 for PUSCH scheduling, Format 1 for single-codeword PDSCH scheduling, Format 1A for compact single-codeword PDSCH scheduling, Format 1C for very compact DL-SCH scheduling, Format 2 for PDSCH scheduling in a closed-loop spatial multiplexing mode, Format 2A for PDSCH scheduling in an open-loop spatial multiplexing mode, and Format 3/3A for transmission of Transmission Power Control (TPC) commands for uplink channels. DCI Format 1A is available for PDSCH scheduling irrespective of the transmission mode of a UE.

The length of PDCCH payload may vary with DCI formats. In addition, the type and length of PDCCH payload may be changed depending on compact or non-compact scheduling or the transmission mode of a UE.

The transmission mode of a UE may be configured for DL data reception on a PDSCH at the UE. For example, DL data carried on a PDSCH includes scheduled data, a paging message, a random access response, broadcast information on a BCCH, etc. for a UE. The DL data of the PDSCH is related to a DCI format signaled through a PDCCH. The transmission mode may be configured semi-statically for the UE by higher-layer signaling (e.g. Radio Resource Control (RRC) signaling). The transmission mode may be classified as single antenna transmission or multi-antenna transmission.

A transmission mode is configured for a UE semi-statically by higher-layer signaling. For example, multi-antenna transmission scheme may include transmit diversity, open-loop or closed-loop spatial multiplexing, Multi-User Multiple Input Multiple Output (MU-MIMO), or beamforming Transmit diversity increases transmission reliability by transmitting the same data through multiple Tx antennas. Spatial multiplexing enables high-speed data transmission without increasing a system bandwidth by simultaneously transmitting different data through multiple Tx antennas. Beamforming is a technique of increasing the Signal to Interference plus Noise Ratio (SINR) of a signal by weighting multiple antennas according to channel states.

A DCI format for a UE depends on the transmission mode of the UE. The UE has a reference DCI format monitored according to the transmission mode configure for the UE. The following 10 transmission modes are available to UEs:

(1) Transmission mode 1: Single antenna port (port 0);

(2) Transmission mode 2: Transmit diversity;

(3) Transmission mode 3: Open-loop spatial multiplexing when the number of layer is larger than 1 or Transmit diversity when the rank is 1;

(4) Transmission mode 4: Closed-loop spatial multiplexing;

(5) Transmission mode 5: MU-MIMO;

(6) Transmission mode 6: Closed-loop rank−1 precoding;

(7) Transmission mode 7: Precoding supporting a single layer transmission, which does not based on a codebook (Rel-8);

(8) Transmission mode 8: Precoding supporting up to two layers, which do not based on a codebook (Rel-9);

(9) Transmission mode 9: Precoding supporting up to eight layers, which do not based on a codebook (Rel-10); and

(10) Transmission mode 10: Precoding supporting up to eight layers, which do not based on a codebook, used for CoMP (Rel-11).

1.2.3 PDCCH Transmission

The eNB determines a PDCCH format according to DCI that will be transmitted to the UE and adds a Cyclic Redundancy Check (CRC) to the control information. The CRC is masked by a unique Identifier (ID) (e.g. a Radio Network Temporary Identifier (RNTI)) according to the owner or usage of the PDCCH. If the PDCCH is destined for a specific UE, the CRC may be masked by a unique ID (e.g. a cell-RNTI (C-RNTI)) of the UE. If the PDCCH carries a paging message, the CRC of the PDCCH may be masked by a paging indicator ID (e.g. a Paging-RNTI (P-RNTI)). If the PDCCH carries system information, particularly, a System Information Block (SIB), its CRC may be masked by a system information ID (e.g. a System Information RNTI (SI-RNTI)). To indicate that the PDCCH carries a random access response to a random access preamble transmitted by a UE, its CRC may be masked by a Random Access-RNTI (RA-RNTI).

Then the eNB generates coded data by channel-encoding the CRC-added control information. The channel coding may be performed at a code rate corresponding to an MCS level. The eNB rate-matches the coded data according to a CCE aggregation level allocated to a PDCCH format and generates modulation symbols by modulating the coded data. Herein, a modulation order corresponding to the MCS level may be used for the modulation. The CCE aggregation level for the modulation symbols of a PDCCH may be one of 1, 2, 4, and 8. Subsequently, the eNB maps the modulation symbols to physical REs (i.e. CCE to RE mapping).

1.2.4 Blind Decoding (BD)

A plurality of PDCCHs may be transmitted in a subframe. That is, the control region of a subframe includes a plurality of CCEs, CCE 0 to CCE NCCE,k−1. NCCE,k is the total number of CCEs in the control region of a kth subframe. A UE monitors a plurality of PDCCHs in every subframe. This means that the UE attempts to decode each PDCCH according to a monitored PDCCH format.

The eNB does not provide the UE with information about the position of a PDCCH directed to the UE in an allocated control region of a subframe. Without knowledge of the position, CCE aggregation level, or DCI format of its PDCCH, the UE searches for its PDCCH by monitoring a set of PDCCH candidates in the subframe in order to receive a control channel from the eNB. This is called blind decoding. Blind decoding is the process of demasking a CRC part with a UE ID, checking a CRC error, and determining whether a corresponding PDCCH is a control channel directed to a UE by the UE.

The UE monitors a PDCCH in every subframe to receive data transmitted to the UE in an active mode. In a Discontinuous Reception (DRX) mode, the UE wakes up in a monitoring interval of every DRX cycle and monitors a PDCCH in a subframe corresponding to the monitoring interval. The PDCCH-monitored subframe is called a non-DRX subframe.

To receive its PDCCH, the UE should blind-decode all CCEs of the control region of the non-DRX subframe. Without knowledge of a transmitted PDCCH format, the UE should decode all PDCCHs with all possible CCE aggregation levels until the UE succeeds in blind-decoding a PDCCH in every non-DRX subframe. Since the UE does not know the number of CCEs used for its PDCCH, the UE should attempt detection with all possible CCE aggregation levels until the UE succeeds in blind decoding of a PDCCH.

In the LTE system, the concept of Search Space (SS) is defined for blind decoding of a UE. An SS is a set of PDCCH candidates that a UE will monitor. The SS may have a different size for each PDCCH format. There are two types of SSs, Common Search Space (CSS) and UE-specific/Dedicated Search Space (USS).

While all UEs may know the size of a CSS, a USS may be configured for each individual UE. Accordingly, a UE should monitor both a CSS and a USS to decode a PDCCH. As a consequence, the UE performs up to 44 blind decodings in one subframe, except for blind decodings based on different CRC values (e.g., C-RNTI, P-RNTI, SI-RNTI, and RA-RNTI).

In view of the constraints of an SS, the eNB may not secure CCE resources to transmit PDCCHs to all intended UEs in a given subframe. This situation occurs because the remaining resources except for allocated CCEs may not be included in an SS for a specific UE. To minimize this obstacle that may continue in the next subframe, a UE-specific hopping sequence may apply to the starting point of a USS.

[Table 4] illustrates the sizes of CSSs and USSs.

TABLE 4 Number of Number of PDCCH Number of candidates in common candidates in dedicated format CCEs (n) search space search space 0 1 — 6 1 2 — 6 2 4 4 2 3 8 2 2

To mitigate the load of the UE caused by the number of blind decoding attempts, the UE does not search for all defined DCI formats simultaneously. Specifically, the UE always searches for DCI Format 0 and DCI Format 1A in a USS. Although DCI Format 0 and DCI Format 1A are of the same size, the UE may distinguish the DCI formats by a flag for format0/format 1a differentiation included in a PDCCH. Other DCI formats than DCI Format 0 and DCI Format 1A, such as DCI Format 1, DCI Format 1B, and DCI Format 2 may be required for the UE.

The UE may search for DCI Format 1A and DCI Format 1C in a CSS. The UE may also be configured to search for DCI Format 3 or 3A in the CSS. Although DCI Format 3 and DCI Format 3A have the same size as DCI Format 0 and DCI Format 1A, the UE may distinguish the DCI formats by a CRC scrambled with an ID other than a UE-specific ID.

An SS S_(k) ^((L)) is a PDCCH candidate set with a CCE aggregation level L∈{1, 2, 4, 8}. The CCEs of PDCCH candidate set m in the SS may be determined by the following equation. L·{(Y _(k) +m)mod └N _(CCE,k) /L┘}+i  [Equation 1]

where M^((L)) is the number of PDCCH candidates with CCE aggregation level L to be monitored in the SS, m=0, . . . , M^((L))−1, i is the index of a CCE in each PDCCH candidate, and i=0, . . . , L−1·k=└n_(s)/2┘ where n_(s) is the index of a slot in a radio frame.

As described before, the UE monitors both the USS and the CSS to decode a PDCCH. The CSS supports PDCCHs with CCE aggregation levels {4, 8} and the USS supports PDCCHs with CCE aggregation levels {1, 2, 4, 8}. [Table 5] illustrates PDCCH candidates monitored by a UE.

TABLE 5 Search space S_(k) ^((L)) Number of PDCCH Type Aggregation level L Size [in CCEs] candidates M^((L)) UE- 1 6 6 specific 2 12 6 4 8 2 8 16 2 Common 4 16 4 8 16 2

Referring to [Equation 1], for two aggregation levels, L=4 and L=8, Y_(k) a is set to 0 in the CSS, whereas Y_(k) is defined by [Equation 2] for aggregation level L in the i USS. Y _(k)=(A·Y _(k-1))mod D  [Equation 2]

where Y⁻¹=n_(RNTI)≠0, n_(RNTI) indicating an RNTI value. A=39827 and D=65537.

1.3 Carrier Aggregation (CA) Environment

1.3.1 CA Overview

A 3GPP LTE system (conforming to Rel-8 or Rel-9) (hereinafter, referred to as an LTE system) uses Multi-Carrier Modulation (MCM) in which a single Component Carrier (CC) is divided into a plurality of bands. In contrast, a 3GPP LTE-A system (hereinafter, referred to an LTE-A system) may use CA by aggregating one or more CCs to support a broader system bandwidth than the LTE system. The term CA is interchangeably used with carrier combining, multi-CC environment, or multi-carrier environment.

In the present disclosure, multi-carrier means CA (or carrier combining). Herein, CA covers aggregation of contiguous carriers and aggregation of non-contiguous carriers. The number of aggregated CCs may be different for a DL and a UL. If the number of DL CCs is equal to the number of UL CCs, this is called symmetric aggregation. If the number of DL CCs is different from the number of UL CCs, this is called asymmetric aggregation. The term CA is interchangeable with carrier combining, bandwidth aggregation, spectrum aggregation, etc.

The LTE-A system aims to support a bandwidth of up to 100 MHz by aggregating two or more CCs, that is, by CA. To guarantee backward compatibility with a legacy IMT system, each of one or more carriers, which has a smaller bandwidth than a target bandwidth, may be limited to a bandwidth used in the legacy system.

For example, the legacy 3GPP LTE system supports bandwidths {1.4, 3, 5, 10, 15, and 20 MHz} and the 3GPP LTE-A system may support a broader bandwidth than 20 MHz using these LTE bandwidths. A CA system of the present disclosure may support CA by defining a new bandwidth irrespective of the bandwidths used in the legacy system.

There are two types of CA, intra-band CA and inter-band CA. Intra-band CA means that a plurality of DL CCs and/or UL CCs are successive or adjacent in frequency. In other words, the carrier frequencies of the DL CCs and/or UL CCs are positioned in the same band. On the other hand, an environment where CCs are far away from each other in frequency may be called inter-band CA. In other words, the carrier frequencies of a plurality of DL CCs and/or UL CCs are positioned in different bands. In this case, a UE may use a plurality of Radio Frequency (RF) ends to conduct communication in a CA environment.

The LTE-A system adopts the concept of cell to manage radio resources. The above-described CA environment may be referred to as a multi-cell environment. A cell is defined as a pair of DL and UL CCs, although the UL resources are not mandatory. Accordingly, a cell may be configured with DL resources alone or DL and UL resources.

For example, if one serving cell is configured for a specific UE, the UE may have one DL CC and one UL CC. If two or more serving cells are configured for the UE, the UE may have as many DL CCs as the number of the serving cells and as many UL CCs as or fewer UL CCs than the number of the serving cells, or vice versa. That is, if a plurality of serving cells are configured for the UE, a CA environment using more UL CCs than DL CCs may also be supported.

CA may be regarded as aggregation of two or more cells having different carrier frequencies (center frequencies). Herein, the term ‘cell’ should be distinguished from ‘cell’ as a geographical area covered by an eNB. Hereinafter, intra-band CA is referred to as intra-band multi-cell and inter-band CA is referred to as inter-band multi-cell.

In the LTE-A system, a Primacy Cell (PCell) and a Secondary Cell (SCell) are defined. A PCell and an SCell may be used as serving cells. For a UE in RRC_CONNECTED state, if CA is not configured for the UE or the UE does not support CA, a single serving cell including only a PCell exists for the UE. On the contrary, if the UE is in RRC_CONNECTED state and CA is configured for the UE, one or more serving cells may exist for the UE, including a PCell and one or more SCells.

Serving cells (PCell and SCell) may be configured by an RRC parameter. A physical-layer ID of a cell, PhysCellId is an integer value ranging from 0 to 503. A short ID of an SCell, SCellIndex is an integer value ranging from 1 to 7. A short ID of a serving cell (PCell or SCell), ServeCellIndex is an integer value ranging from 1 to 7. If ServeCellIndex is 0, this indicates a PCell and the values of ServeCellIndex for SCells are pre-assigned. That is, the smallest cell ID (or cell index) of ServeCellIndex indicates a PCell.

A PCell refers to a cell operating in a primary frequency (or a primary CC). A UE may use a PCell for initial connection establishment or connection reestablishment. The PCell may be a cell indicated during handover. In addition, the PCell is a cell responsible for control-related communication among serving cells configured in a CA environment. That is, PUCCH allocation and transmission for the UE may take place only in the PCell. In addition, the UE may use only the PCell in acquiring system information or changing a monitoring procedure. An Evolved Universal Terrestrial Radio Access Network (E-UTRAN) may change only a PCell for a handover procedure by a higher-layer RRCConnectionReconfiguraiton message including mobilityControlInfo to a UE supporting CA.

An SCell may refer to a cell operating in a secondary frequency (or a secondary CC). Although only one PCell is allocated to a specific UE, one or more SCells may be allocated to the UE. An SCell may be configured after RRC connection establishment and may be used to provide additional radio resources. There is no PUCCH in cells other than a PCell, that is, in SCells among serving cells configured in the CA environment.

When the E-UTRAN adds an SCell to a UE supporting CA, the E-UTRAN may transmit all system information related to operations of related cells in RRC_CONNECTED state to the UE by dedicated signaling. Changing system information may be controlled by releasing and adding a related SCell. Herein, a higher-layer RRCConnectionReconfiguration message may be used. The E-UTRAN may transmit a dedicated signal having a different parameter for each cell rather than it broadcasts in a related SCell.

After an initial security activation procedure starts, the E-UTRAN may configure a network including one or more SCells by adding the SCells to a PCell initially configured during a connection establishment procedure. In the CA environment, each of a PCell and an SCell may operate as a CC. Hereinbelow, a Primary CC (PCC) and a PCell may be used in the same meaning and a Secondary CC (SCC) and an SCell may be used in the same meaning in embodiments of the present disclosure.

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, which are used in embodiments of the present disclosure.

FIG. 6(a) illustrates a single carrier structure in the LTE system. There are a DL CC and a UL CC and one CC may have a frequency range of 20 MHz.

FIG. 6(b) illustrates a CA structure in the LTE-A system. In the illustrated case of FIG. 6(b), three CCs each having 20 MHz are aggregated. While three DL CCs and three UL CCs are configured, the numbers of DL CCs and UL CCs are not limited. In CA, a UE may monitor three CCs simultaneously, receive a DL signal/DL data in the three CCs, and transmit a UL signal/UL data in the three CCs.

If a specific cell manages N DL CCs, the network may allocate M (M≤N) DL CCs to a UE. The UE may monitor only the M DL CCs and receive a DL signal in the M DL CCs. The network may prioritize L (L≤M≤N) DL CCs and allocate a main DL CC to the UE. In this case, the UE should monitor the L DL CCs. The same thing may apply to UL transmission.

The linkage between the carrier frequencies of DL resources (or DL CCs) and the carrier frequencies of UL resources (or UL CCs) may be indicated by a higher-layer message such as an RRC message or by system information. For example, a set of DL resources and UL resources may be configured based on linkage indicated by System Information Block Type 2 (SIB2). Specifically, DL-UL linkage may refer to a mapping relationship between a DL CC carrying a PDCCH with a UL grant and a UL CC using the UL grant, or a mapping relationship between a DL CC (or a UL CC) carrying HARQ data and a UL CC (or a DL CC) carrying an HARQ ACK/NACK signal.

1.3.2 Cross Carrier Scheduling

Two scheduling schemes, self-scheduling and cross carrier scheduling are defined for a CA system, from the perspective of carriers or serving cells. Cross carrier scheduling may be called cross CC scheduling or cross cell scheduling.

In self-scheduling, a PDCCH (carrying a DL grant) and a PDSCH are transmitted in the same DL CC or a PUSCH is transmitted in a UL CC linked to a DL CC in which a PDCCH (carrying a UL grant) is received.

In cross carrier scheduling, a PDCCH (carrying a DL grant) and a PDSCH are transmitted in different DL CCs or a PUSCH is transmitted in a UL CC other than a UL CC linked to a DL CC in which a PDCCH (carrying a UL grant) is received.

Cross carrier scheduling may be activated or deactivated UE-specifically and indicated to each UE semi-statically by higher-layer signaling (e.g. RRC signaling).

If cross carrier scheduling is activated, a Carrier Indicator Field (CIF) is required in a PDCCH to indicate a DL/UL CC in which a PDSCH/PUSCH indicated by the PDCCH is to be transmitted. For example, the PDCCH may allocate PDSCH resources or PUSCH resources to one of a plurality of CCs by the CIF. That is, when a PDCCH of a DL CC allocates PDSCH or PUSCH resources to one of aggregated DL/UL CCs, a CIF is set in the PDCCH. In this case, the DCI formats of LTE Release-8 may be extended according to the CIF. The CIF may be fixed to three bits and the position of the CIF may be fixed irrespective of a DCI format size. In addition, the LTE Release-8 PDCCH structure (the same coding and resource mapping based on the same CCEs) may be reused.

On the other hand, if a PDCCH transmitted in a DL CC allocates PDSCH resources of the same DL CC or allocates PUSCH resources in a single UL CC linked to the DL CC, a CIF is not set in the PDCCH. In this case, the LTE Release-8 PDCCH structure (the same coding and resource mapping based on the same CCEs) may be used.

If cross carrier scheduling is available, a UE needs to monitor a plurality of PDCCHs for DCI in the control region of a monitoring CC according to the transmission mode and/or bandwidth of each CC. Accordingly, an appropriate SS configuration and PDCCH monitoring are needed for the purpose.

In the CA system, a UE DL CC set is a set of DL CCs scheduled for a UE to receive a PDSCH, and a UE UL CC set is a set of UL CCs scheduled for a UE to transmit a PUSCH. A PDCCH monitoring set is a set of one or more DL CCs in which a PDCCH is monitored. The PDCCH monitoring set may be identical to the UE DL CC set or may be a subset of the UE DL CC set. The PDCCH monitoring set may include at least one of the DL CCs of the UE DL CC set. Or the PDCCH monitoring set may be defined irrespective of the UE DL CC set. DL CCs included in the PDCCH monitoring set may be configured to always enable self-scheduling for UL CCs linked to the DL CCs. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring set may be configured UE-specifically, UE group-specifically, or cell-specifically.

If cross carrier scheduling is deactivated, this implies that the PDCCH monitoring set is always identical to the UE DL CC set. In this case, there is no need for signaling the PDCCH monitoring set. However, if cross carrier scheduling is activated, the PDCCH monitoring set may be defined within the UE DL CC set. That is, the eNB transmits a PDCCH only in the PDCCH monitoring set to schedule a PDSCH or PUSCH for the UE.

FIG. 7 illustrates a cross carrier-scheduled subframe structure in the LTE-A system, which is used in embodiments of the present disclosure.

Referring to FIG. 7, three DL CCs are aggregated for a DL subframe for LTE-A UEs. DL CC ‘A’ is configured as a PDCCH monitoring DL CC. If a CIF is not used, each DL CC may deliver a PDCCH that schedules a PDSCH in the same DL CC without a CIF. On the other hand, if the CIF is used by higher-layer signaling, only DL CC ‘A’ may carry a PDCCH that schedules a PDSCH in the same DL CC ‘A’ or another CC. Herein, no PDCCH is transmitted in DL CC ‘B’ and DL CC ‘C’ that are not configured as PDCCH monitoring DL CCs.

2. Control Signal Transmission Through PUCCH (Physical Uplink Control Channel)

The PUCCH is an uplink control channel used to transmit uplink control information (UCI). The UCI transmitted on the PUCCH includes scheduling request (SR) information, HARQ ACK/NACK information and CQI information.

The amount of control information which a UE can transmit in a subframe depends on the number of SC-FDMA symbols available for transmission of control signaling data (at this time, excluding SC-FDMA symbols used for transmission of reference signals used for coherent detection of the PUCCH). The LTE/LTE-A system supports 7 different PUCCH formats depending on information which will be signaled on the PUCCH.

PUCCH may include the following formats to transmit control information.

(1) Format 1: On-Off keying (OOK) modulation, used for SR (Scheduling Request)

(2) Format 1a & 1b: Used for ACK/NACK transmission

-   -   1) Format 1a: BPSK ACK/NACK for 1 codeword     -   2) Format 1b: QPSK ACK/NACK for 2 codewords

(3) Format 2: QPSK modulation, used for CQI transmission

(4) Format 2a & Format 2b: Used for simultaneous transmission of CQI and ACK/NACK

(5) Format 3: Used for multiple ACK/NACK transmission in a carrier aggregation environment

Table 6 shows a modulation scheme according to PUCCH format and the number of bits per subframe. Table 7 shows the number of reference signals (RS) per slot according to PUCCH format. Table 8 shows SC-FDMA symbol location of RS (reference signal) according to PUCCH format. In Table 6, PUCCH format 2a and PUCCH format 2b correspond to a case of normal cyclic prefix (CP).

TABLE 6 PUCCH format Modulation scheme No. of bits per subframe, Mbit 1  N/A N/A 1a BPSK 1 1b QPSK 2 2  QPSK 20 2a QPSK + BPSK 21 2b QPSK + BPSK 22 3  QPSK 48

TABLE 7 PUCCH format Normal CP Extended CP 1, 1a, 1b 3 2 2 2 1 2a, 2b 2 N/A

TABLE 8 PUCCH SC-FDMA symbol location of RS format Normal CP Extended CP 1, 1a, 1b 2, 3, 4 2, 3 2, 3 1, 5 3 2a, 2b 1, 5 N/A

FIG. 8 is a diagram illustrating physical mapping of a PUCCH format into PUCCH RBs.

Referring to FIG. 8, PUCCH formats 2/2a/2b are mapped and allocated to edge RBs of a PUCCH band (for example, PUCCH region m=0, 1), and then PUCCH RB where PUCCH formats 2/2a/2b are combined with PUCCH formats 1/1a/1b is allocated (for example, PUCCH region m=2). Next, the PUCCH formats 1/1a/1b are allocated to the PUCCH RBs (for example, PUCCH region m=3, 4, 5). Information on the number N of PUCCH RBs used for the PUCCH formats 2/2a/2b is transferred from the cell to the UEs by a broadcast signal. FIG. 8 illustrates an example of PUCCH formats which are allocated, wherein the PUCCH formats actually mapped onto the PUCCH can be allocated sequentially in accordance with the aforementioned order.

2. 1 CQI Transmission Through PUCCH Format

FIG. 9 is a diagram illustrating PUCCH formats 2/2a/2b in case of a normal cyclic prefix, and FIG. 10 is a diagram illustrating PUCCH formats 2/2a/2b in case of an extended cyclic prefix.

The periodicity and frequency resolution used by a UE to report CQI are both controlled by the eNB. In the time domain, both periodic and aperiodic CQI reporting are supported. The PUCCH format 2 is used for periodic CQI reporting only, and the PUSCH is used for aperiodic reporting of the CQI. At this time, the eNB especially commands CQI reporting to the UE, and the UE transmits CQI report to a resource which is scheduled for uplink data transmission.

The PUCCH CQI channel structure for one slot in case of a normal CP will be understood with reference to FIG. 9. In this case, SC-FDMA symbols 1 and 5 (i.e., the second and sixth symbols) are used for DM RS (Demodulation Reference Signal) transmission. The PUCCH CQI channel structure for one slot in case of an extended CP will be understood with reference to FIG. 10. In this case, SC-FDMA symbol 3 is used for DM RS transmission. The DM-RS is a reference signal transmitted by the UE to the uplink and may be referred to as UL RS.

CQI information of 10 bits channel coded with a ½ coding rate is punctured by (20, k) Reed-Muller (RM) code to give 20 coded bits. Afterwards, the CQI information is scrambled (for example, scrambled in a similar way to PUSCH data with a length-31 Gold sequence) prior to QPSK constellation mapping. One QPSK modulated symbol is transmitted to each of the 10 SCFDMA symbols in the subframe by modulating a cyclic time shift of the base RS sequence of length-12 prior to OFDM modulation. The 12 equally-spaced cyclic time shifts allow 12 different UEs to be orthogonally multiplexed on the same CQI PUCCH RB. The DM RS sequence is similar to the frequency domain CQI signal sequence but does not include CQI data modulation.

The UE is configured to periodically report different CQI, PMI, and RI types on CQI PUCCH by receiving a higher layer signal that includes a PUCCH resource index n_(PUCCH) ⁽²⁾, which indicates both the cyclic time shift and the PUCCH region which will be used.

2.2 HARQ ACK/NACK Transmission Through PUCCH Format 1

FIG. 11 is a diagram illustrating PUCCH formats 1a/1b in case of a normal cyclic prefix, and FIG. 12 is a diagram illustrating PUCCH formats 1a/1b in case of an extended cyclic prefix.

Referring to FIGS. 11 and 12, three SC-FDMA symbols in the middle of the slot are used for UL-RS in case of the normal CP, and two SC-FDMA symbols in the middle of the slot are used for UL-RS in case of the extended CP. At this time, both 1- and 2-bit ACK/NACKs are modulated using BPSK and QPSK modulation, respectively.

In case of CQI transmission, the one BPSK/QPSK modulated symbol is transmitted on each SC-FDMA data symbol by modulating a cyclic time shift of the base RS sequence of length-12 (i.e. frequency-domain CDM) prior to OFDM modulation. In addition, time-domain spread codes with orthogonal (Walsh-Hadamard of DFT) spreading codes are used to code-division-multiplex UEs. The RSs from the different UEs are multiplexed in the same way as the data SC-FDMA symbols.

2. 3 Multiplexing of CQI and ACK/NACK

In the LTE system, simultaneous transmission of HARQ ACK/NACK and CQI is enabled by UE-specific higher layer signaling.

In the case that simultaneous transmission is not enabled and that the UE is configured to report CQI on the PUCCH of the same subframe that needs HARQ ACK/NACK transmission, CQI report is dropped and only HARQ ACK/NACK is transmitted using the PUCCH format 1a/1b.

In the case that simultaneous transmission is enabled, the CQI and the 1- or 2-bit ACK/NACK information need to be multiplexed on the same PUCCH RB while maintaining the low CM (Cubic Metric) single carrier property. The methods used to achieve this are different for the case of normal CP and extended CP.

In the case of the normal CP, to transmit a 1- or 2-bit HARQ ACK/NACK together with CQI, the ACK/NACK bits (which are not scrambled) are BPSK/QPSK modulated as shown in FIG. 13, resulting in a single HARQ ACK/NACK modulation symbol d_(HARQ). FIG. 13 is a diagram illustrating one of constellation mapping of HARQ ACK/NACK for a normal CP. At this time, an ACK signal is encoded as a binary ‘1’ and a NACK signal is encoded as a binary ‘0’. The single HARQ ACK/NACK modulation symbol, d_(HARQ), is then used to modulate the second RS symbol (SC-FDMA symbol 5, i.e., RS signaled by ACK/NACK) in each CQI slot. That is, ACK/NACK is signaled using the corresponding RS.

In case of the extended CP with one RS symbol per slot, the 1- or 2-bit HARQ ACK/NACK is jointly encoded with the CQI resulting in a (20, k_(CQI)+k_(A/N)) Reed-Muller based block code. A 20-bit codeword is transmitted on the PUCCH that uses the CQI channel structure of FIG. 9. The joint coding of the ACK/NACK and CQI is performed as shown in FIG. 14. The largest number of information bits supported by the block code is 13. At this time, k_(CQI)=11 CQI bits and k_(A/N)=2 bits.

2.4 Multiplexing of SR and ACK/NACK

FIG. 15 is a diagram illustrating one of methods for multiplexing SR and ACK/NACK signal, and FIG. 16 is a diagram illustrating constellation mapping of ACK/NACK and SR for PUCCH formats 1/1a/1b.

Referring to FIG. 15, if an SR signal and an ACK/NACK signal are simultaneously transmitted at the same subframe, the UE transmits the ACK/NACK signal on the SR PUCCH resource allocated for a positive SR or transmits ACK/NACK on the ACK/NACK PUCCH resource allocated in case of a negative SR. The constellation mapping for simultaneous transmission of ACK/NACK and SR is shown in FIG. 16.

2. 5 HARQ ACK/NACK Transmission in TDD System

In case of LTE TDD (Time Division Multiplexing), since the UE can receive PDSCHs during a plurality of subframes, the UE can feed HARQ ACK/NACK for multiple PDSCHs back to the eNB. That is, there are two types of HARQ ACK/NACK transmission schemes as follows.

(1) ACK/NACK Bundling

With ACK/NACK bundling, ACK/NACK responses for multiple data units are combined by logical-AND operation. For example, if the Rx node (or receiver) decodes all the data units successfully, the Rx node transmits ACK using one ACK/NACK unit. Otherwise, if the Rx node fails in decoding any of the data units, the Rx node may either transmit NACK using one ACK/NACK unit or transmit nothing for ACK/NACK.

(2) ACK/NACK Multiplexing

With ACK/NACK multiplexing, contents of the ACK/NACK responses for multiple data units are identified by the combination of the ACK/NACK unit used in actual ACK/NACK transmission and the one of QPSK modulation symbols. For example, if it is assumed that one ACK/NACK unit carries two bits and two data units are transmitted in maximum, the ACK/NACK result can be identified at the TX node as illustrated in the following Table 9.

TABLE 9 HARQ-ACK(0), HARQ-ACK(1) n_(PUCCH) ⁽¹⁾ b(0), b(1) ACK, ACK n_(PUCCH, 1) ⁽¹⁾ 1, 1 ACK, NACK/DTX n_(PUCCH, 0) ⁽¹⁾ 0, 1 NACK/DTX, ACK n_(PUCCH, 1) ⁽¹⁾ 0, 0 NACK/DTX, NACK n_(PUCCH, 1) ⁽¹⁾ 1, 0 NACK, DTX n_(PUCCH, 0) ⁽¹⁾ 1, 0 DTX, DTX N/A N/A

In Table 9, HARQ-ACK(i) indicates the ACK/NACK result for the data unit i (there are maximum 2 data units, that is, data unit 0 and data unit 1 in this example). In Table 9, DTX means there is no data unit transmitted for corresponding HARQ-ACK(i) or the Rx node does not detect the existence of the data unit corresponding to HARQ-ACK(i). n_(PUCCH,X) ⁽¹⁾ indicates the ACK/NACK unit which is used in actual ACK/NACK transmission, where there are two ACK/NACK units, n_(PUCCH,0) ⁽¹⁾ and n_(PUCCH,1) ⁽¹⁾ in maximum.

b(0),b(1) indicates two bits carried by the selected ACK/NACK unit. Modulation symbol which is transmitted through ACK/NACK unit is decided in accordance with the bits. For example, if the RX node receives and decodes two data units successfully, the Rx node transmits two bits, (1, 1), using ACK/NACK unit n_(PUCCH,1) ⁽¹⁾. For another example, if the Rx node receives two data units, fails in decoding of the first data unit (corresponding to HARQ-ACK(0)), and decodes the second data unit (corresponding to HARQ-ACK(1)) successfully, the RX node transmits two bits (0, 0) using n_(PUCCH,1) ⁽¹⁾.

By linking the actual ACK/NACK contents with the combination of ACK/NACK unit selection and the actual bit contents used for transmission of the ACK/NACK unit, ACK/NACK transmission using single ACK/NACK unit for multiple data units is possible. The example described in Table 9 can be extended to the ACK/NACK transmission for more than 2 data units.

In ACK/NACK multiplexing method, NACK and DTX are coupled as NACK/DTX as shown in Table 9 if at least one ACK exists for all data units. This is because that combinations of ACK/NACK unit and QPSK symbol are insufficient to cover all ACK/NACK hypotheses based on decoupling of NACK and DTX. On the other hand, for the case that no ACK exists for all data units (in other words, NACK or DTX only exists for all data units), single definite NACK case is defined as the case that only one of HARQ-ACK(i) is NACK decoupled with DTX. In this case, ACK/NACK unit linked to the data unit corresponding to single definite NACK can also be reserved to transmit the signal of multiple ACK/NACKs.

When the maximum number of data units which can be transmitted within a given amount of physical resources becomes larger, the required ACK/NACK hypotheses for ACK/NACK multiplexing over all the data units may exponentially increase. Denoting the maximum number of data units and the number of corresponding ACK/NACK units as N and N_(A), respectively, 2^(N) ACK/NACK hypotheses are required for ACK/NACK multiplexing even if DTX case is precluded. On the other hand, applying the single ACK/NACK unit selection as described above, ACK/NACK multiplexing can be supported by up to 4N_(A) ACK/NACK hypotheses.

In other words, as the number of data units increases, the single ACK/NACK unit selection requires relatively larger amount of ACK/NACK units which yields increased overhead of control channel resources required to transmit the signal for multiple ACK/NACKs. For example, if 5 data units (N=5) are used for transmission, 8 ACK/NACK units (N_(A)=8) should be available for ACK/NACK transmission because the required number of ACK/NACK hypotheses for ACK/NACK multiplexing is 2^(N)=32 (=4N_(A)).

2. 6 Uplink Channel Coding for PUCCH Format 2

In LTE uplink transmission, certain control channels are encoded using a linear block code as illustrated in Table 10.

TABLE 10 i M_(i,0) M_(i,1) M_(i,2) M_(i,3) M_(i,4) M_(i,5) M_(i,6) M_(i,7) M_(i,8) M_(i,9) M_(i,10) M_(i,11) M_(i,12) 0 1 1 0 0 0 0 0 0 0 0 1 1 0 1 1 1 1 0 0 0 0 0 0 1 1 1 0 2 1 0 0 1 0 0 1 0 1 1 1 1 1 3 1 0 1 1 0 0 0 0 1 0 1 1 1 4 1 1 1 1 0 0 0 1 0 0 1 1 1 5 1 1 0 0 1 0 1 1 1 0 1 1 1 6 1 0 1 0 1 0 1 0 1 1 1 1 1 7 1 0 0 1 1 0 0 1 1 0 1 1 1 8 1 1 0 1 1 0 0 1 0 1 1 1 1 9 1 0 1 1 1 0 1 0 0 1 1 1 1 10 1 0 1 0 0 1 1 1 0 1 1 1 1 11 1 1 1 0 0 1 1 0 1 0 1 1 1 12 1 0 0 1 0 1 0 1 1 1 1 1 1 13 1 1 0 1 0 1 0 1 0 1 1 1 1 14 1 0 0 0 1 1 0 1 0 0 1 0 1 15 1 1 0 0 1 1 1 1 0 1 1 0 1 16 1 1 1 0 1 1 1 0 0 1 0 1 1 17 1 0 0 1 1 1 0 0 1 0 0 1 1 18 1 1 0 1 1 1 1 1 0 0 0 0 0 19 1 0 0 0 0 1 1 0 0 0 0 0 0

If input bits to the linear block code is denoted as a₀, a₁, a₂, . . . , a_(A), after encoding the bits are denoted by b₀, b₁, b₂, . . . , b_(B) where B=20. The following Equation 3 indicates one of methods for generating encoded bits.

$\begin{matrix} {{b_{i} = {\left( {\sum\limits_{n = 0}^{A - 1}\left( {a_{n} \cdot M_{i,n}} \right)} \right){mod}\; 2}},{{{where}\mspace{14mu} i} = 0},1,2,\ldots\mspace{14mu},{B - 1.}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack \end{matrix}$

The encoded bits then are mapped to code-time-frequency resource as shown in FIG. 17. FIG. 17 is a diagram illustrating methods of matching control information with a physical resource region. The first 10 encoded bits are mapped a specific code-time-frequency resource, and the last 10 encoded bits are mapped to a different code-time-frequency resource. At this time, the frequency spacing between first 10 encoded bits and the last 10 encoded bits are usually large, whereby frequency diversity for the encoded bits can be obtained.

2. 7 Uplink Channel Coding in LTE-A System

As described above, in the LTE system (that is, Rel-8), if UCI is transmitted to a PUCCH format 2, (20, A) RM coding of Table 10 is performed for CSI of maximum 13 bits. However, if the UCI is transmitted to the PUSCH, (32, A) RM coding of Table 11 is performed for CQI of maximum 11 bits, and truncation or cyclic repetition is performed to match a code rate which will be transmitted to the PUSCH.

TABLE 11 i M_(i,0) M_(i,1) M_(i,2) M_(i,3) M_(i,4) M_(i,5) M_(i,6) M_(i,7) M_(i,8) M_(i,9) M_(i,10) 0 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 0 1 1 2 1 0 0 1 0 0 1 0 1 1 1 3 1 0 1 1 0 0 0 0 1 0 1 4 1 1 1 1 0 0 0 1 0 0 1 5 1 1 0 0 1 0 1 1 1 0 1 6 1 0 1 0 1 0 1 0 1 1 1 7 1 0 0 1 1 0 0 1 1 0 1 8 1 1 0 1 1 0 0 1 0 1 1 9 1 0 1 1 1 0 1 0 0 1 1 10 1 0 1 0 0 1 1 1 0 1 1 11 1 1 1 0 0 1 1 0 1 0 1 12 1 0 0 1 0 1 0 1 1 1 1 13 1 1 0 1 0 1 0 1 0 1 1 14 1 0 0 0 1 1 0 1 0 0 1 15 1 1 0 0 1 1 1 1 0 1 1 16 1 1 1 0 1 1 1 0 0 1 0 17 1 0 0 1 1 1 0 0 1 0 0 18 1 1 0 1 1 1 1 1 0 0 0 19 1 0 0 0 0 1 1 0 0 0 0 20 1 0 1 0 0 0 1 0 0 0 1 21 1 1 0 1 0 0 0 0 0 1 1 22 1 0 0 0 1 0 0 1 1 0 1 23 1 1 1 0 1 0 0 0 1 1 1 24 1 1 1 1 1 0 1 1 1 1 0 25 1 1 0 0 0 1 1 1 0 0 1 26 1 0 1 1 0 1 0 0 1 1 0 27 1 1 1 1 0 1 0 1 1 1 0 28 1 0 1 0 1 1 1 0 1 0 0 29 1 0 1 1 1 1 1 1 1 0 0 30 1 1 1 1 1 1 1 1 1 1 1 31 1 0 0 0 0 0 0 0 0 0 0

In the LTE-A system, a PUCCH format 3 has been introduced to transmit UCI (A/N and SR) bits of maximum 21 bits, and in the status of the normal CP, the UE may transmit code bits of 48 bits by using the PUCCH format 3. Therefore, when the number of UCI bits is 11 bits or less, (32, A) RM coding is used, and in this case, cyclic repetition of code bits is used to correspond to code bits required by the PUCCH format 3. If the number of UCI bits exceeds 11 bits, the number of (32, A) RM code based sequences in Table 11 is not sufficient, whereby two code bits are generated using two (32, A) RM coding blocks as illustrated in FIG. 18 (this case will be referred to as Dual RM), and the other bits are transmitted by truncation and interleaving to reduce the two code bits to correspond to the number of code bits of the PUCCH format 3.

In the case that the UCI of maximum 21 bits is transmitted to the PUSCH, truncation or cyclic repetition is performed using (32, A) RM coding in the same manner as the legacy Rel-8 system to match a code rate which will be transmitted to the PUSCH when the number of UCI bits is 11 bits or less, whereas two coded bits are generated using Dual RM when the number of UCI bits exceeds 11 bits, and truncation or cyclic repetition is performed for the two coded bits to match the code rate which will be transmitted to the PUSCH.

Referring to FIG. 18, when the number of input UCI bits corresponds to 21 bits, the transmitter generates a part 1 and a part 2 by dividing the corresponding UCI bits. Afterwards, the transmitter applies (32, A) RM coding to each of the part 1 and the part 2, and truncates or cyclically repeats the code bits to match with 48 bits that can be transmitted by the PUCCH format 3. Then, the transmitter interleaves or concatenates code bits which are output, whereby the code bits can be transmitted through the PUCCH format 3.

In more detail, a bit configuration order per UCI will be described. If the PUCCH format 3 is configured to be used for an SR transport subframe, when SR and A/N are transmitted to the PUCCH format 3 or the PUSCH, the A/N is first arranged and then the SR is arranged next to the A/N, whereby UCI bits are configured.

FIG. 19 is a diagram illustrating a method for interleaving output code bits when dual RM described in FIG. 18 is used. Referring to FIG. 19, when data blocks (that is, UCI) of lengths A and B are respectively input to (32, A) and (32, B) RM encoders, the output code bits are subjected to rate matching of 24 bits to become A0, A1, . . . , A23 and B0, B1, . . . , B23.

The code bits A0, A1, . . . , A23 and B0, B1, . . . , B23 are input to an interleaver, and the code bits output from the interleaver are output in pairs in due order to generate bit streams of A0, A1, B0, B1, A2, A3, B2, B3, . . . , A22, A23, B22 and B23. The bit streams are QPSK modulated and transmitted in accordance with a PUCCH format 3 transport format, wherein the first 24 bits (12 QPSK symbols) of the bit streams are mapped into a first slot and the other 24 bits (12 QPSK symbols) are mapped into a second slot.

3. Spatial Modulation

Spatial Modulation (SM) is to represent selection of antennas or antenna group with some of input bit streams in a wireless access system that supports a UE and an eNB, each of which includes a plurality of antennas, and transmit the other bit streams through mapping on a constellation point.

FIG. 20 is a diagram illustrating a concept of a spatial modulation scheme.

FIG. 20(a) illustrates that 3 bits are transmitted using four transmitting (Tx) antennas of a transmitter. At this time, first 2 bits of 3 bit streams represent one of four transmitting antennas, and the other 1 bit may be transmitted by BPSK modulation. Meanwhile, FIG. 20(b) illustrates that first 1 bit of 3 bit streams is used to select one of two transmitting antennas and the other 2 bits are transmitted by QPSK modulation when there are two transmitting antennas in the transmitter.

2 bits of FIG. 20(a) and 1 bit of FIG. 20(b), which are used for antenna selection, are not actually transmitted from the transmitter to the receiver. However, if the receiver detects an antenna through which a signal or symbol received therein is transmitted, the receiver may identify the corresponding bits.

That is, referring to FIG. 20, if there are four transmitting antennas, information of 2 bits may indicate each antenna, and if there are two transmitting antennas, information of 1 bit may indicate each antenna. Therefore, the receiver may detect specific information of 2 bits or 1 bit by identifying an antenna through which a signal is transmitted.

Therefore, if the number of transmitting antennas is increased, the number of bits required to select antennas in the transmitter is increased, whereby the amount of data or control information matched with the corresponding bits is increased. In this respect, the SM scheme is suitable for the antenna transmission technology such as massive MIMO.

The receiver may detect an antenna or antenna group for data signals transmitted using the SM scheme and then decode the received data by performing demodulation. At this time, the receiver may use a decision metric as expressed in the Equation 4 to detect the antenna or antenna group that has transmitted the data signals. Y1=r1·h*=|h| ² d+h*·n,r1=h·d1+n Y2=r2·g*=g*·n,r2=g·d2+n  [Equation 4]

In the Equation 4, Y1 indicates a decision metric for the antenna (port) that has transmitted the data signals, and Y2 indicates a decision metric for an antenna (port) that has not transmitted the data signals. At this time, r1 and r2 mean received symbols, h and g mean radio channels to which the corresponding received symbols are subjected, d1 and d2 mean noise of the data signals which are actually transmitted, and n means noise of the corresponding radio channel.

The receiver may identify whether data signals of a kth antenna or antenna group have been transmitted, through Z(k)=max (Y1, Y2). Therefore, the receiver may decide a transmitting antenna through which the data signals are transmitted, if k=max Z(k), k=1, . . . , M (M: # of transmit antennas). After detecting the antenna or antenna group, the receiver may demodulate the received data through a demodulation procedure.

When the transmitter transmits data/control signals by using the SM scheme, the transmitting antennas may be individual antennas or antenna group, or may be individual antenna ports or antenna port group. In the embodiments of the present invention, for convenience of description, it is assumed that the transmitting antennas are individual antennas. However, the embodiments of the present invention may equally be applied to even a case where the transmitting antennas configure an antenna group.

3. 1 Method of Link Adaptation for SM Scheme

If the SM scheme is used, some of bit streams to be transmitted from the transmitter is used for antenna selection, and the other bit streams are used for data transmission. At this time, a plurality of transmitting antennas may have their respective channel features different from one another. In this case, a link adaptation method may be considered as follows.

(1) Method 1: Method for applying the same modulation and coding scheme (MCS) to data transmitted from all antennas or all antenna groups.

(2) Method 2: Method for applying respective MCSs different from one another to data transmitted per antenna or antenna group.

In case of the method 1, it is advantageous in that CSI feedback can be reduced, however, an MCS level is determined depending on the worst channel, whereby whole data throughput can be reduced. In case of the method 2, it is advantageous in that an MCS level optimized for a state of each channel can be set, however, overhead for performing CSI feedback per channel may be increased.

Therefore, the method 1 may be used for a case where a channel status is good, while the method 2 may be used for a case where the channel status is not good. Also, the method 1 ad the method 2 may be used semi-static change.

3. 2 Spatial Modulation Scheme Based on Spatial Multiplexing

Hereinafter, a method for extending an SM scheme to a spatial multiplexing scheme will be suggested. However, for convenience of description, it is assumed that the number of transmitting antennas of the transmitter is 4. Methods which will be described hereinafter may equally be applied to even a case where the number of transmitting antennas is 2, 3, or 5 or more.

For example, in case of rank 1 transmission, since the transmitter selects and transmits one of four transmitting antennas, the number of bits additionally transmitted when the SM scheme is used may be set to

$\left\lfloor {\log_{2}\begin{pmatrix} 4 \\ 1 \end{pmatrix}} \right\rfloor.$ That is, the transmitter may select antennas with 2 bits, and may transmit the other bits by mapping the other bits into a constellation point.

In this way, in case of rank 2, since the transmitter selects two transmitting antennas and transmits data signals, bits corresponding to

$\left\lfloor {\log_{2}\begin{pmatrix} 4 \\ 2 \end{pmatrix}} \right\rfloor$ are used to select the transmitting antennas and the other bit streams are transmitted by modulation.

Also, in case of rank 3, the transmitter may select three transmitting antennas by using

$\left\lfloor {\log_{2}\begin{pmatrix} 4 \\ 3 \end{pmatrix}} \right\rfloor$ and transmit the other bit streams through modulation. However, in case of rank 4, since the transmitter transmits the data signals by using all the antennas, the data bit streams may be transmitted by modulation without antenna selection.

FIG. 21 is a diagram illustrating one of methods for transmitting and receiving data/control signals by using a spatial modulation (SM) scheme to which spatial multiplexing is applied.

The aforementioned Equation 4 relates to a method for detecting an antenna that has transmitted data, in a receiver if spatial multiplexing is not used. Hereinafter, a method for transmitting and receiving data/control signals if spatial multiplexing is used will be described.

Referring to FIG. 21, the transmitter configures data signals or control signals by applying the SM scheme. That is, the transmitter may configure the data signals by using data bits which will be transmitted and information bits added by antenna selection (S2110).

At this time, since the transmitter uses a spatial multiplexing scheme, data streams corresponding to one or more ranks can be transmitted. However, in this case, the receiver should know information on a rank of data streams transmitted from the transmitter, so as to identify the number of antenna ports of the transmitter. Therefore, the transmitter transmits rank information to the receiver. At this time, the rank information may be transmitted through a downlink control signal (for example, PDCCH signal) (S2120).

The transmitter may transmit the data and control signals configured in the step S2110 and a reference signal (for example, DM-RS (Demodulation Reference Signal) used for a specific UE to the receiver (S2130).

The DM-RS which is the UE specific signal is used for PDSCH signal transmission, and a different DM-RS is used for each antenna port. Therefore, the receiver may identify an antenna port through which the data signals are transmitted, during DM-RS reception. The receiver may identify the number of antenna ports which have been used for SM data transmission, on the basis of the rank information and the DMRS, which are received in the steps S2120 and S2130, exactly detect transmitting antenna ports (S2140).

The receiver may derive the bit streams used for antenna selection on the basis of the rank information and the antenna ports, which are received and detected in the step S2130. Therefore, the receiver may demodulate the data signals or the control signals transmitted from the base station on the basis of the decoded signal and the derived bit streams (S2150).

If the UE specific reference signal is used in the step S2130 of FIG. 21, it is preferable that the control signal which is transmitted is an E-PDCCH (Enhanced PDCCH) transmitted from a PDSCH region.

In case of the LTE/LTE-A system, the bit streams configure OFDM symbols, a plurality of OFDM symbols (e.g., six or seven symbols) configure one slot, and one subframe is configured by two slots. Therefore, if the SM scheme is applied to the LTE/LTE-A system, the SM scheme may be applied in a unit of bit streams, OFDM symbols, slot, or subframe.

For example, if the SM scheme is applied to the LTE/LTE-A system in a unit of bit streams, it is advantageous in that bits used for selection of transmitting antennas are additionally transmitted in addition to modulation symbols. Likewise, if the SM scheme is applied to the LTE/LTE-A system in a unit of OFDM symbols, in addition to bits corresponding to OFDM symbols, bits used for selection of transmitting antennas may additionally be transmitted. If the SM scheme is applied to the LTE/LTE-A system in a unit of slot or subframe, data signals equivalent to the number of bits required to select transmitting antennas or antenna ports may additionally be transmitted every slot or every subframe. For example, if the SM scheme is applied to the LTE/LTE-A system in a unit of subframe and the transmitter uses two transmitting antennas, it is advantageous in that the transmitter additionally transmits 1 bit. At this time, the added 1 bit may be used for transmission of data or control information.

3. 3 Method for Transmitting Control Information

The case where the control signals are transmitted together with the DM-RS has been described with reference to FIG. 21. In this case, it is preferable that the control signals are E-PDCCH signals. The E-PDCCH signals may be transmitted even in case of the SM scheme described in the clause 3.1, and the SM scheme may be applied to even transmission of a PDCCH signal which is a normal control signal.

Hereinafter, a method for transmitting control information by using an SM scheme will be described.

3. 3. 1 PHICH Transmission Based on SM Scheme

The E-PDCCH signal is transmitted through a PDSCH region. The transmitter may select one of a plurality of antennas to transmit the E-PDCCH. At this time, the transmitter may transmit a PHICH signal by using bits required to select one of the plurality of antennas.

For example, if the transmitter includes two transmitting antennas, the transmitter may use 1 bit, which is required to select transmitting antennas, to transmit a PHICH which is an ACK/NACK response to a PUSCH. That is, a set of EPDCCH candidates is configured to include antenna ports 107 and 109. In this case, if the E-PDCCH signal is transmitted through the antenna port 107, ACK for the PUSCH may be set, and if the E-PDCCH signal is transmitted through the antenna port 109, NACK for the PUSCH may be set. At this time, it may be assumed that the E-PDCCH signal is control information having PDSCH scheduling information for a UE which is scheduled with the PUSCH.

In more detail, the transmitter that has received the PDSCH signal from the receiver detects ACK/NACK for the corresponding PDSCH signal. Afterwards, the transmitter may transmit the E-PDCCH signal together with PHICH information by using the SM scheme when transmitting the E-PDCCH signal instead of transmitting a separate PHICH signal. That is, the transmitter may select one of a plurality of antennas to transmit the E-PDCCH signal and transmit PHICH information to the receiver by using one or more bits required for selection of the corresponding antenna. Therefore, the receiver may know PHICH information by detecting the antenna port to which the E-PDCCH signal is transmitted.

3. 3. 2 Method for Transmitting NDI Information

The transmitter may transmit new data indicator (NDI) bits of bits for configuring a DCI format of the E-PDCCH signal by using the SM scheme. For example, the transmitter may transmit NDI information by carrying the NDI information in the bits used for selection of the transmitting antennas. If the E-PDCCH signal is transmitted through the antenna port 107 of the transmitter, it may mean ‘NDI=not toggled (i.e., re-transmission)’. If the E-PDCCH signal is transmitted through the antenna port 109 of the transmitter, it may mean ‘NDI=toggled (i.e., new transmission)’. Therefore, the receiver may acquire NDI information by detecting the antenna through which the received E-PDCCH signal is transmitted. In this way, the transmitter may reduce a size of a DCI format that configures the E-PDCCH signal.

3. 3. 3 Method for Transmitting TPC Information

Transmit power control (TPC) bits of information bits configuring the DCI format of the E-PDCCH signal may be transmitted using spatial modulation. For example, the transmitter may transmit TPC information bits by using bits used to select the transmitting antenna for transmitting the E-PDCCH signal. If the E-PDCCH signal is transmitted through the antenna port 107, it corresponds to a ‘TPC=UP (power up)’ command. Also, if the E-PDCCH signal is transmitted through the antenna port 109, it may be configured to mean a ‘TPC=DOWN (power down)’ command.

Therefore, the receiver may acquire TPC information by detecting the antenna through which the received E-PDCCH signal is transmitted. In this way, the transmitter may reduce the size of the DCI format that configures the E-PDCCH signal.

3. 4 Method for Transmitting Data Signals

Channel coding is applied to a general communication system during data transmission. Also, the LTE/LTE-A system adopts turbo coding during channel coding. Code bits encoded using a turbo encoder are categorized into systematic bits (S) and parity bits (P).

Hereinafter, a case where the SM scheme is applied to systematic bits and parity bits, which configure data signals, will be described. Generally, decoding performance is more affected by the systematic bits than the parity bits. Therefore, if the systematic bits are transmitted more reliably than the parity bits, it is helpful to improve decoding performance of the data signals. In this respect, if the SM scheme is applied, the transmitter may additionally transmit bit streams, which are used to select the transmitting antennas, to the bit streams mapped into modulation symbols.

A demodulation procedure of the receiver for the modulation symbols is performed after the transmitting antenna that has transmitted the modulation symbols is detected. Therefore, the systematic bits may be arranged in the bits for selecting the transmitting antenna to improve data transmission performance. The transmitter may match the parity bits with the modulation symbols after the bits used to select the transmitting antenna are all used for the systematic bits.

FIG. 22 is a diagram illustrating a method for applying a spatial modulation (SM) scheme to systematic bits and parity bits, which configure data signals. Particularly, FIG. 22(a) relates to a method for transmitting systematic bits by using bits for antenna selection and transmitting parity bits through modulation as described above. Unlike FIG. 22(a), FIG. 22(b) illustrates a method for transmitting parity bits by matching the parity bits with bits for antenna selection and transmitting systematic bits through modulation.

In case of FIG. 22(b), the receiver detects a transmitting antenna through which data signals are transmitted, when detecting the data signals received therein. A method for detecting the transmitting antenna may be performed using the aforementioned Equation 4 or the method described with reference to FIG. 21. The receiver that has detected the transmitting antenna may detect bits for selecting the corresponding transmitting antenna, and may detect the parity bits through the detected bits. Afterwards, the receiver may demodulate the systematic bits by demodulating the received data signals.

FIG. 23 is a diagram illustrating one of methods for configuring data signals in a transmitter by applying a spatial modulation (SM) scheme.

It is assumed that the transmitter includes two transmitting antennas or two transmitting antenna groups. If the transmitting antennas are configured by two groups, the number of antennas which belong to each group may be the same as each other or different from each other.

Referring to FIG. 23, the SM scheme is applied to code bit streams, which are ⅓ turbo-coded, comprised of systematic bits of 16 bits and parity bits of 32 bits. The bit streams shown in FIG. 23 may be transmitted using the method described in FIG. 22. If the systematic bits or the parity bits are transmitted using an antenna selection scheme, ‘0’ means a data bit mapped into an antenna port ‘x’, and ‘1’ means a data bit mapped into an antenna port ‘y’. The data bits which do not use the antenna selection scheme are transmitted by being modulated through a modulation scheme provided by a modulator.

FIG. 24 is a diagram illustrating examples of methods for transmitting turbo code bits by applying a spatial modulation (SM) scheme to the turbo code bits.

FIG. 24(a) illustrates a method for modulating parity bits P1 and P2 by concatenating them in series, and FIG. 24(b) illustrates a method for modulating parity bits P1 and P2 by concatenating them in parallel. For convenience of description, the methods of FIG. 24 are shown using the parity bits shown in FIG. 23. Also, the methods of FIG. 24 may be applied when the systematic bits are transmitted to the receiver as additional bits according to the antenna selection scheme in accordance with the SM scheme described in FIG. 22(a) and parity bits are modulated.

If the bits in the methods of FIG. 24 are transmitted in accordance with the SM scheme described in FIG. 22(b) and one of P1 and P2 is only transmitted in accordance with the antenna selection scheme, P1 or P2 and the systematic bits may be modulated by concatenation in the way described in FIG. 24.

The aforementioned embodiments of the present invention have been described based on that the transmitter is an eNB and the receiver is a UE. However, the aforementioned embodiments may equally or similarly be applied to even a case where the transmitter is a UE and the receiver is an eNB. For example, in case of transmission of the PUSCH signal for transmitting ACK/NACK for the PDSCH signal, ACK/NACK signal may be transmitted in accordance with the SM scheme. Also, uplink control information may be transmitted through the SM scheme.

In case of the methods for transmitting control signals or control information by using the SM scheme described in the clause 3.3, the number of bits of control information which will be transmitted is not great. Therefore, the corresponding SM scheme may be applied to even a case where the number of transmitting antennas is small. In this respect, the methods described in the clause 3.3 may be applied to the legacy LTE/LTE-A system. However, in the methods for transmitting data signals as described in the clause 3.4, it is general that the number of data bits which will be transmitted is great. Therefore, the methods of the clause 3.4 may be used in a massive MIMO environment or small cell environment.

4. Apparatuses

Apparatuses illustrated in FIG. 25 are means that can implement the methods described before with reference to FIGS. 1 to 24.

A UE may act as a transmitting end on a UL and as a receiving end on a DL. An eNB may act as a receiving end on a UL and as a transmitting end on a DL.

That is, each of the UE and the eNB may include a transmitter (Tx) 2540 or 2550 and a Receiver (Rx) 2560 or 2570, for controlling transmission and reception of information, data, and/or messages, and an antenna 2500 or 2510 for transmitting and receiving information, data, and/or messages.

Each of the UE and the eNB may further include a processor 2520 or 2530 for implementing the afore-described embodiments of the present disclosure and a memory 2580 or 2590 for temporarily or permanently storing operations of the processor 2520 or 2530.

The embodiments of the present invention can be performed using the elements and functions of the aforementioned UE and the aforementioned eNB. For example, the processor of the UE and the eNB can transmit data bits or control information by applying the SM scheme by means of combination of the methods described in the aforementioned clauses 1 to 3. Its details will be understood with reference to the clause 3.

The Tx and Rx of the UE and the eNB may perform a packet modulation/demodulation function for data transmission, a high-speed packet channel coding function, OFDMA packet scheduling, TDD packet scheduling, and/or channelization. Each of the UE and the eNB of FIG. 25 may further include a low-power Radio Frequency (RF)/Intermediate Frequency (IF) module.

Meanwhile, the UE may be any of a Personal Digital Assistant (PDA), a cellular phone, a Personal Communication Service (PCS) phone, a Global System for Mobile (GSM) phone, a Wideband Code Division Multiple Access (WCDMA) phone, a Mobile Broadband System (MB S) phone, a hand-held PC, a laptop PC, a smart phone, a Multi Mode-Multi Band (MM-MB) terminal, etc.

The smart phone is a terminal taking the advantages of both a mobile phone and a PDA. It incorporates the functions of a PDA, that is, scheduling and data communications such as fax transmission and reception and Internet connection into a mobile phone. The MB-MM terminal refers to a terminal which has a multi-modem chip built therein and which can operate in any of a mobile Internet system and other mobile communication systems (e.g. CDMA 2000, WCDMA, etc.).

Embodiments of the present disclosure may be achieved by various means, for example, hardware, firmware, software, or a combination thereof.

In a hardware configuration, the methods according to exemplary embodiments of the present disclosure may be achieved by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

In a firmware or software configuration, the methods according to the embodiments of the present disclosure may be implemented in the form of a module, a procedure, a function, etc. performing the above-described functions or operations. A software code may be stored in the memory 2580 or 2590 and executed by the processor 2520 or 25330. The memory is located at the interior or exterior of the processor and may transmit and receive data to and from the processor via various known means.

Those skilled in the art will appreciate that the present disclosure may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present disclosure. The above embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the invention should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. It is obvious to those skilled in the art that claims that are not explicitly cited in each other in the appended claims may be presented in combination as an embodiment of the present disclosure or included as a new claim by a subsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to various wireless access systems including a 3GPP system, a 3GPP2 system, and/or an IEEE 802.xx system. Besides these wireless access systems, the embodiments of the present disclosure are applicable to all technical fields in which the wireless access systems find their applications. 

What is claimed is:
 1. A method for transmitting data signals from a transmitter by using a spatial modulation (SM) scheme in a wireless access system, the method performed an enhanced Node-B (eNB) and comprising: selecting two or more transmitting antennas for transmitting the data signals by using two or more ranks; deriving data bit streams by applying the SM scheme, wherein the data bit streams correspond to the two or more ranks; configuring the data signals by using the SM scheme on the basis of the data bit streams; transmitting, to a user equipment (UE), an enhanced physical downlink control channel (E-PDCCH) and demodulation reference signals (DM-RSs) through one of the two or more transmitting antennas, the E-PDCCH including rank information indicating a number of rank used for transmitting the data signals; and transmitting, to the UE, the configured data signals through the selected two or more transmitting antennas and DM-RSs matched with each of the selected two or more transmission antennas, wherein each of the two or more transmission antennas uses different predetermined DM-RSs from each other, wherein combinations of the rank information and the DM-RSs identify each of the two or more transmission antennas, wherein, if the E-PDCCH is transmitted through a first transmission antenna of the two or more transmission antennas, this represents a positive acknowledgment (ACK) for uplink data transmitted from the UE, and wherein, if the E-PDCCH is transmitted through a second transmission antenna of the two or more transmission antennas, this represents a negative acknowledgement (NACK) for the uplink data transmitted from the UE.
 2. The method according to claim 1, wherein when a new data indicator (NDI) or transmission power control (TPC) information is mapped into the data bit streams according to the SM scheme, the E-PDCCH does not include the NDI or the TPC information, respectively.
 3. The method according to claim 1, wherein systematic bits of input bits are mapped into the data bits according to the SM scheme.
 4. The method according to claim 1, wherein parity bits of input bits are mapped into the data bits according to the SM scheme.
 5. A method for receiving data signals in a receiver by using a spatial modulation (SM) scheme in a wireless access system, the method performed by a user equipment (UE) and comprising: receiving, from an enhanced Node-B (eNB), an enhanced physical downlink control channel (E-PDCCH) and demodulation reference signals (DM-RSs) that are transmitted through one of two or more transmitting antennas of the eNB that are selected by the eNB for transmitting data signals by using two or more ranks, the E-PDCCH including rank information indicating a number of rank used by the eNB for transmitting the data signals; receiving, from the eNB, the data signals along with DM-RSs matched with each of the two or more transmission antennas of the eNB; detecting antenna ports of the eNB, from which the received data signals are transmitted, respectively, by using the rank information and the DM-RSs; deriving data bit streams according to the detected antenna ports; and demodulating the received data signals on the basis of the data bit streams, wherein each of the two or more transmission antennas uses different predetermined DM-RSs from each other, wherein combinations of the rank information and the DM-RSs identify each of the two or more transmission antennas, wherein, if the E-PDCCH is transmitted through a first transmission antenna of the two or more transmission antennas of the eNB, this represents a positive acknowledgment (ACK) for uplink data transmitted from the UE, and wherein, if the E-PDCCH is transmitted through a second transmission antenna of the two or more transmission antennas, this represents a negative acknowledgement (NACK) for the uplink data transmitted from the UE.
 6. The method according to claim 5, wherein when a new data indicator (NDI) or transmission power control (TPC) information is mapped into the data bit streams according to the SM scheme, the E-PDCCH does not include the NDI and the TPC information, respectively.
 7. The method according to claim 5, wherein systematic bits of input bits are mapped into the data bit streams according to the SM scheme.
 8. The method according to claim 5, wherein parity bits of input bits are mapped into the data bit streams according to the SM scheme.
 9. A user equipment (UE) for receiving data signals by using a spatial modulation (SM) scheme in a wireless access system, the UE comprising: an antenna; a receiver; and a processor operatively connected to the receiver and the antenna, the processor configured to: receive, from an enhanced Node-B (eNB), an enhanced physical downlink control channel (E-PDCCH) and demodulation reference signals (DM-RSs) that are transmitted through one of two or more transmitting antennas of the eNB that are selected by the eNB for transmitting data signals by using two or more ranks, the E-PDCCH including rank information indicating a number of rank used by the eNB for transmitting the data signals; receive, from the eNB, the data signals along with DM-RSs matched with each of the two or more transmission antennas of the eNB; detect antenna ports of the eNB, from which the received data signals are transmitted, respectively, by using the rank information and the DM-RSs; derive data bit streams according to the detected antenna ports; and demodulate the received data signals on the basis of the data bit streams, wherein each of the two or more transmission antennas uses different predetermined DM-RSs from each other, wherein combinations of the rank information and the DM-RSs identify each of the two or more transmission antennas, wherein, if the E-PDCCH is transmitted through a first transmission antenna of the two or more transmission antennas of the eNB, this represents a positive acknowledgment (ACK) for uplink data transmitted from the UE, and wherein, if the E-PDCCH is transmitted through a second transmission antenna of the two or more transmission antennas, this represents a negative acknowledgement (NACK) for the uplink data transmitted from the UE. 